Auto merge of #17103 - aneeshusa:shim-subprocess-devnull, r=larsbergstrom
Auto merge of #17103 - aneeshusa:shim-subprocess-devnull, r=larsbergstrom

Shim subprocess.DEVNULL for Python 2

This was introduced in Python 3.3, so provide our own version.

Requires careful review since this will leak secrets (!!!) if not done properly.

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- [ ] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes help with #17045 (github issue number if applicable).

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- [ ] There are tests for these changes OR
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fiji-flo/servo,dati91/servo,fiji-flo/servo,mbrubeck/servo,eddyb/servo,szeged/servo,pyfisch/servo,rnestler/servo,szeged/servo,splav/servo,paulrouget/servo,sadmansk/servo,peterjoel/servo,DominoTree/servo,mattnenterprise/servo,DominoTree/servo,notriddle/servo,fiji-flo/servo,szeged/servo,thiagopnts/servo,upsuper/servo,peterjoel/servo,DominoTree/servo,fiji-flo/servo,CJ8664/servo,pyfisch/servo,ConnorGBrewster/servo,SimonSapin/servo,notriddle/servo,nnethercote/servo,notriddle/servo,SimonSapin/servo,CJ8664/servo,saneyuki/servo,notriddle/servo,mbrubeck/servo,sadmansk/servo,pyfisch/servo,dsandeephegde/servo,KiChjang/servo,ConnorGBrewster/servo,ConnorGBrewster/servo,paulrouget/servo,szeged/servo,paulrouget/servo,KiChjang/servo,canaltinova/servo,splav/servo,upsuper/servo,eddyb/servo,szeged/servo,pyfisch/servo,nnethercote/servo,avadacatavra/servo,pyfisch/servo,anthgur/servo,canaltinova/servo,anthgur/servo,eddyb/servo,nnethercote/servo,paulrouget/servo,KiChjang/servo,thiagopnts/servo,peterjoel/servo,paulrouget/servo,jimberlage/servo,CJ8664/servo,peterjoel/servo,upsuper/servo,cbrewster/servo,nnethercote/servo,SimonSapin/servo,nnethercote/servo,ConnorGBrewster/servo,dsandeephegde/servo,szeged/servo,saneyuki/servo,peterjoel/servo,larsbergstrom/servo,avadacatavra/servo,emilio/servo,larsbergstrom/servo,dati91/servo,emilio/servo,mbrubeck/servo,dsandeephegde/servo,SimonSapin/servo,anthgur/servo,larsbergstrom/servo,emilio/servo,dati91/servo,splav/servo,thiagopnts/servo,DominoTree/servo,pyfisch/servo,notriddle/servo,CJ8664/servo,thiagopnts/servo,mattnenterprise/servo,eddyb/servo,paulrouget/servo,dati91/servo,nnethercote/servo,CJ8664/servo,rnestler/servo,splav/servo,KiChjang/servo,anthgur/servo,canaltinova/servo,dsandeephegde/servo,larsbergstrom/servo,DominoTree/servo,SimonSapin/servo,peterjoel/servo,sadmansk/servo,KiChjang/servo,notriddle/servo,upsuper/servo,ConnorGBrewster/servo,cbrewster/servo,splav/servo,dsandeephegde/servo,KiChjang/servo,notriddle/servo,thiagopnts/servo,anthgur/servo,sadmansk/servo,rnestler/servo,emilio/servo,ConnorGBrewster/servo,DominoTree/servo,anthgur/servo,saneyuki/servo,avadacatavra/servo,canaltinova/servo,mattnenterprise/servo,avadacatavra/servo,saneyuki/servo,peterjoel/servo,emilio/servo,SimonSapin/servo,avadacatavra/servo,sadmansk/servo,emilio/servo,szeged/servo,ConnorGBrewster/servo,mbrubeck/servo,splav/servo,anthgur/servo,KiChjang/servo,rnestler/servo,fiji-flo/servo,dati91/servo,emilio/servo,anthgur/servo,jimberlage/servo,CJ8664/servo,saneyuki/servo,emilio/servo,cbrewster/servo,jimberlage/servo,dati91/servo,emilio/servo,jimberlage/servo,SimonSapin/servo,larsbergstrom/servo,larsbergstrom/servo,nnethercote/servo,mattnenterprise/servo,fiji-flo/servo,dsandeephegde/servo,peterjoel/servo,upsuper/servo,larsbergstrom/servo,mbrubeck/servo,cbrewster/servo,cbrewster/servo,saneyuki/servo,rnestler/servo,eddyb/servo,dati91/servo,pyfisch/servo,notriddle/servo,sadmansk/servo,pyfisch/servo,saneyuki/servo,szeged/servo,DominoTree/servo,sadmansk/servo,splav/servo,thiagopnts/servo,nnethercote/servo,mattnenterprise/servo,paulrouget/servo,KiChjang/servo,mbrubeck/servo,pyfisch/servo,saneyuki/servo,cbrewster/servo,mattnenterprise/servo,mbrubeck/servo,rnestler/servo,thiagopnts/servo,mbrubeck/servo,paulrouget/servo,jimberlage/servo,saneyuki/servo,mattnenterprise/servo,eddyb/servo,fiji-flo/servo,emilio/servo,canaltinova/servo,pyfisch/servo,paulrouget/servo,mattnenterprise/servo,upsuper/servo,avadacatavra/servo,DominoTree/servo,eddyb/servo,dati91/servo,canaltinova/servo,DominoTree/servo,fiji-flo/servo,jimberlage/servo,KiChjang/servo,dsandeephegde/servo,avadacatavra/servo,thiagopnts/servo,larsbergstrom/servo,dsandeephegde/servo,upsuper/servo,avadacatavra/servo,saneyuki/servo,ConnorGBrewster/servo,canaltinova/servo,notriddle/servo,larsbergstrom/servo,SimonSapin/servo,canaltinova/servo,cbrewster/servo,jimberlage/servo,upsuper/servo,jimberlage/servo,eddyb/servo,notriddle/servo,nnethercote/servo,jimberlage/servo,szeged/servo,cbrewster/servo,splav/servo,splav/servo,rnestler/servo,CJ8664/servo,KiChjang/servo,peterjoel/servo,larsbergstrom/servo,nnethercote/servo,paulrouget/servo,splav/servo,CJ8664/servo,peterjoel/servo,DominoTree/servo,sadmansk/servo,szeged/servo,rnestler/servo